Two-stroke cycle engine of the sleeve valve type



Feb. 4, 11. s KAMMER 2,239,407

TWO-STROKE CYCLE ENGINE OF THE SLEEVE VALVE TYPE Filed Oct. 14, 1939 2 Sheets-Sheet 1 Feb. 4, 1941. s KAMMER 2,230,4Q7

TWO-STROKE CYCLE ENGINE OF THE SLEEVE VALVE 'il YPE Filed Oct. 14, 19159 2 Sheets-Sheet 2 Patented Feb. 4, 1941 UNITED STATES TWO-STROKE CYCLE ENGINE OF THE. SLEEVE VALVE TYPE George Stephen Kammer, Park Lane, London, England Application October 14, 1939, Serial No. 299,550 In Great Britain January 21, 1939 4 Claims.

The invention relates to engines operating on the two stroke cycle in which control is eflfected by a single sleeve valve of the Burt-McCollum type, that is a valve in which the path of movement of any point is an oval.

The invention relates more particularly to the shape of the cooperating ports in the cylinder and sleeve valve and is of especial advantage when applied to an engine constructed in accordance with the specification of British Patent No. 506,326. The principal object of the invention is to provide rapid opening of the admission ports at the right time, but as further objects there may be mentioned rapid closing of the admission ports and-suitable correlation of the opening and closing of the various ports.

According to the invention the inlet ports in the cylinder wall each comprise an opening edge having an oblique portion transverse to the instantaneous direction of movement of the sleeve at the commencement of admission and located on a re-entrant portion of the port, the ports in the sleeve having corresponding opening edges.

The exhaust ports in the cylinder wall are on the contrary rectangular and are controlled by the edge of the sleeve away from the crankshaft. These ports are then at a different level from the admission ports.

In four stroke sleeve valve engines it has been proposed to give the sleeve valve a non-uniform movement and to shape the admission and exhaust ports near the inner end of the sleeve and cylinder wall so that the opening edge comprised an oblique portion between two axial portions. In another proposal the opening edges The present invention is restricted to two stroke engines, and here the conditions are different. The inlet ports must be at the opposite end of the cylinder to the exhaust ports to permit the scavenging air to perform its function. The asymmetrical timing in two stroke engines also necessitates making the closing edge of the port transverse, i. e. circumferential in relation to the cylinder.

The accompanying drawings serve to illustrate the invention and therein Figure 1 is a curve in which the stroke of the sleeve is plotted against crank angle,

Figures 2 to 8 show the ports developed into a plane,

Figure 9 is an axial section of the cylinder to show the exhaust ports and the driving mechanism for the sleeve valve, and

Figure '19 is a section on the line X-X of Figure 9.

Referring first to Figures 9 and 10 for an outline of the type of engine to which the invention is applicable, a cylinder ll, of which only a part is shown, has a ring of rectangular exhaust ports i2 located a little below the head l3. The admission ports 2. are also arranged in a ring but at a lower level. The shape of the admission ports will be described later. A sleeve valve I4 10 controls the ports. The upper edge of the sleeve enters a recess l5 between the cylinder and the head when in its uppermost position, and this edge controls the exhaust ports 52. The sleeve is also provided with admission ports 3 to 00- 15 operate with the cylinder ports 2, these also being of a particular shape to be described later.

The sleeve is driven from the crank shaft 56 by gearing providing a combined rotational and axial movement in which the axial component is such that the sleeve is below its mid position for considerably less than half the duration of each cycle. A gear wheel ll keyed to the crank shaft l6 meshes with an equal gear wheel i8 journaled in the crank casing l9 by roller bearings IS. A slipper 29 is mounted to slide along a diameter of the gear wheel l8 and engages a crank pin 2| on a driving member 22 mounted in peripheral roller bearings 22 in the crank casing i9. The centre line of the driving mem- 30 her 22 is above that of the gear wheel iii.

A slider 23 is adapted to slide in a recess in the axial direction of the driving member 22 and by a spherical seating engages a spherical projection 24 on the sleeve i4. Owing to the eccen- 5 tricity of the driving member 22 in relation to the gear wheel i8, the driving member rotates with a cyclic variation ofspeed. The speed is lowest when the slipper 29 is at the top position and the highest when it is at the bottomposi- 40 tion. The movement of the sleeve I4 corresponds with that of the driving member 22, being slower in the upper part of its path than in the lower part.

In Figure l the stroke of the sleeve is plotted to a scale representing percentage of piston stroke. The total travel is 44%, while the outer half of the travel, viz. 22% of the piston stroke, occurs over about 110 of crank angle. This 50 non-sinusoidal travel can be obtained by means of the valve mechanism described in the patent specification referred to above and recapitulated in the foregoing descriptive paragraphs. It is the kind of movement of the valve for which the port arrangement illustrated and claimed is intended.

The admission ports are arranged around the cylinder wall at appropriate spacing. Figure 2 shows two adjacent ports I- and 2 in full lines, while Figure 3 is so placed that the cylinder port 2 therein also represents in position the next port to 2 in Figure 2. The admission ports in the sleeve are spaced similarly to those in the cylinder wall, and one of them is shown in chain dotted lines at 3 in Figure 2.

The principal part of what has been termed the opening edge of the port I is the part marked BC; this part is oblique and is located on the reentrant portion ABCD of the port. The port 3 in the valve has a similarly shaped edge A'B'C'D', which Just fits the edge ABCD in the position of Figure 2, where admission is about to commence.

The path of the point B on the edge of'the valve port is in the present case approximately an ellipse as shown by the dotted line 4. The centre of the ellipse is at C and its major axis along the line CD.

As already indicated, the lower half of the elliptic path is traversed in about one-third of the time taken for the whole path. The position of Figure 2 in the present example is about 15 of crank angle after the point B has passed the end of the minor axis of the ellipse, the latter being the point at which exhaust commences. The exhaust ports are closed when the point B comes to the other end of the minor axis.

Figure 3 shows the position another 15 of crank angle later. The piston, being near the dead centre, has moved a very'short proportion of its stroke, while the considerable port area shown hatched has been uncovered. It will be noted also that the direction of movement of the sleeve is shown by the position of the point B, which in Figure 2 was at B. The ellipse 4 also gives this direction at the point B in Figure 2. The part BC of the edge is made transverse to the direction of movement so defined, and in the example shown it is nearly perpendicular thereto. After a further 15 of crank angle the position is that of Figure 4, where almost the whole port area is effective. The remaining figures show the position at successive crank angles of 15', and in Figure 5 the port area is still almost all effective. In Figure 6 the area has begun to diminish a little, but the reduction proceeds at an increasing speed, until the effective area is quite small in Figure 7 and is just closing in Figure 8.

The port 3 has a part projecting to the right in the figures, which is of some assistance in increasing the rapidity of opening, as may be seen by reference to Figures 2 and 3. The principal object of this part of the port is, however, shown in Figure 8. This is to cooperate with a supercharger port 5 in the cylinder wall. Soon after the port 3 has uncovered the port 5 the former is withdrawn to the left due to the rotation of the valve sleeve on its axis, closing the port 5 again. Of course the cylinder wall is provided with a series of ports 5 at similar spacings to the ports 2.

The exhaust ports l2 at the inner end of the cylinder are of the ordinary rectangular pattern, the bridges between the ports' being provided only for mechanical reasons. The control of the exhaust is carried out solely by the upper edge of the sleeve valve and is not in any way dependent on the movement of the upper edge of the piston. One result of this is that packingrings abovetheexhaustportscanbedispensed with, reducing the height of the engine.

What I claim is:

1. In atwostrokeinternal engine I with sleeve valve of the Burt-llcCollum type a port arrangement comprising rectangular exhaust ports in the cylinder wall controlled by the edge of the sleeve remote from the engine crankshaft, inlet ports in the cylinder wall each 10 withanopeningedgehavinganaxialpartand a circumferential part joined by an oblique part, and inlet ports in the sleeve having correspondmg opening edges, the movement of the point on the sleeve at which the circumferential part 18 and the oblique part of the opening edge of the port join being substantially an ellipse having its major axis along the axial part of the said edge and its centre at the point where the axial and oblique parts thereof join.

2. In a two stroke internal combustion engine with sleeve valve of the Burt-McCollum type a. port arrangement comprising rectangular exhaust ports in the cylinder wall controlled by the edge of the sleeve remote from the engine crankshaft, inlet ports in the cylinder wall each with an opening edge having an axial part and a circumferential part joined by an oblique part, the movement of the point on the sleeve at which the circumferential part and the oblique part of the opening edge of the port join being substantially an ellime having its major axis along the axial part of the said edge and its centre at the point where the axial and oblique parts thereof join, and the valve timing being such that the exhaust opens and closes when the point at which the circumferential and oblique parts of the opening edge of the sleeve inlet port join passes the two ends respectively of the minor axis of the said ellipse.

3. In a two stroke internal combustion engine with sleeve valve of the Burt-llcCollum type a port arrangement comprising rectangular exhaust ports in the cylinder wall controlled by the edge of the sleeve remote from the engine crankshaft, inlet ports in the cylinder wall each with an opening edge having an oblique portion transverse to the instantaneous direction of movement of the sleeve at the commencement of admission and located on a re-entrant portion of the port, supercharger ports in the cylinder wa l located further from the crankshaft than the inlet ports, and inlet ports in the sleeve having opening edges corresponding to those of the. cylinder inlet portsand having extended parts 5 located to cooperate with the supercharger ports on the closing of the inlet ports.

4. In a two.stroke internal combustion engine with sleeve valve of the Burt-McCollum type a port arrangement comprising rectangular exhaust ports in the cylinder wall controlled by the edge of the sleeve remote from the engine crankshaft, inlet ports in the cylinder wall eachwithanopeningedgehavinganaxial and a circumferential portion and therebetween an oblique portion transverse to the instantaneous direction of movement of the sleeve at the commencement of admission to constitute a reentrant portion of the port, and inlet ports in the sleeve having corresponding re-entrant opening edges, the various ports being controlled solely by the movement of the sleeve without the intervention of the engine piston.

GEORGE 

